Publication number | US6856393 B2 |
Publication type | Grant |
Application number | US 10/378,591 |
Publication date | Feb 15, 2005 |
Filing date | Mar 3, 2003 |
Priority date | Aug 21, 2002 |
Fee status | Paid |
Also published as | CA2495062A1, EP1530712A2, EP1530712B1, US7050169, US7236246, US7236247, US7365851, US20040044714, US20040133614, US20060132783, US20060139645, US20070211253, WO2004019018A2, WO2004019018A3 |
Publication number | 10378591, 378591, US 6856393 B2, US 6856393B2, US-B2-6856393, US6856393 B2, US6856393B2 |
Inventors | Aydogan Ozcan, Michel J.F. Digonnet, Gordon S. Kino |
Original Assignee | The Board Of Trustees Of The Leland Stanford University |
Export Citation | BiBTeX, EndNote, RefMan |
Patent Citations (10), Non-Patent Citations (24), Referenced by (14), Classifications (15), Legal Events (5) | |
External Links: USPTO, USPTO Assignment, Espacenet | |
This application is a continuation-in-part of, and claims priority to, U.S. patent application Ser. No. 10/357,275, filed Jan. 31, 2003, which is incorporated by reference in its entirety herein. U.S. patent application Ser. No. 10/357,275 claims priority to U.S. Provisional Application No. 60/405,405, filed Aug. 21, 2002, which is also incorporated by reference in its entirety herein.
1. Field of the Invention
The present invention relates generally to the field of measuring attributes of a physical system, and more particularly to methods of measuring a non-symmetric physical function.
2. Description of the Related Art
Various optical devices are based on induced second-order susceptibilities in silica-based glass waveguides (e.g., electro-optic modulators, switches, parametric amplifiers). For example, G. Bonfrate et al. describe optical parametric oscillators useful for the study of quantum interference and quantum cryptography, and for metrology applications in Parametric Fluorescence in Periodically Poled Silica Fibers, Applied Physics Letters, Vol. 75, No. 16, 1999, pages 2356-2358, which is incorporated in its entirety by reference herein. Second-order susceptibility can be induced in a several-microns-thick region of fused silica (a material that is not normally centro-symmetric, and therefore normally does not exhibit a second-order susceptibility) by poling at elevated temperatures. This phenomenon has been described by R. A. Myers et al. in Large Second-Order Nonlinearity in Poled Fused Silica, Optics Letters, Vol. 16, No. 22, 1991, pages 1732-1734, which is incorporated in its entirety by reference herein.
The field of poled silica has suffered from the lack of a common method to reliably measure the second-order optical nonlinearity profile of poled samples. This absence of a reliable procedure for measuring nonlinearity profiles may be the reason, at least in part, for wide discrepancies in the measured magnitudes and the positions of the nonlinearity profiles of various poled systems as reported in the literature. The Maker fringe (MF) technique is the most common method currently used to investigate the nonlinearity profile of poled silica. The MF technique comprises focusing a pulsed laser beam of intensity I_{1 }(known as the fundamental signal) onto a sample at an incident angle θ and measuring the intensity I_{2 }of the second harmonic (SH) signal generated within the nonlinear region as a function of the incident angle θ. For a transverse magnetic (TM) polarized fundamental laser beam, the conversion efficiency η_{TM}(θ) is given by:
where
The function ƒ(θ, n_{1}, n_{2}) accounts for both the power loss due to reflection suffered by the fundamental and the SH beams, and the projection of the input electric field along the appropriate direction. In general, ƒ(θ, n_{1}, n_{2}) depends on both the polarization of the input fundamental wave and the geometry of the second harmonic generation configuration. The exact formula of ƒ(θ, n_{1}, n_{2}) is given by D. Pureur, et al. in Absolute Measurement of the Second-Order Nonlinearity Profile in Poled Silica, Optics Letters, Vol. 23, 1998, pages 588-590, which is incorporated in its entirety by reference herein. This phenomenon is also described by P. D. Maker et al. in Effects of Dispersion and Focusing on the Production of Optical Harmonics, Physics Review Letters, Vol. 8, No. 1, 1962, pages 21-22, which is incorporated in its entirety by reference herein.
The conversion efficiency η_{TM}(θ) is obtained experimentally by rotating the sample with respect to the incident laser beam and measuring the power of the SH signal as a function of the incident angle θ. Due to dispersion of the laser beam, Δk is finite and η_{TM}(θ) exhibits oscillations (called the Maker fringes) which pass through several maxima and minima. The objective of this measurement is to retrieve the second-order nonlinearity profile d_{33}(z). The absolute value of the integral in Equation 1 is the amplitude of the Fourier transform of d_{33}(z). In principle, if one knew both the amplitude and the phase of a Fourier transform, one can readily infer the argument of the Fourier transform (in this case d_{33}(z)) by taking the inverse Fourier transform of the Fourier transform. However, the measured Maker fringes provide only the magnitude of the Fourier transform, not its phase. Consequently, for an arbitrary and unknown nonlinearity profile, the MF measurement alone is not sufficient to determine a unique solution for d_{33}(z). Even if the phase information were available, it would provide the shape of d_{33}(z) but it would still not provide the location of this shape beneath the surface of the sample (i.e., where the nonlinearity profile starts beneath the surface).
Previous efforts to determine d_{33}(z) have involved fitting various trial profiles to the measured MF data. Examples of such efforts are described by M. Qiu et al. in Double Fitting of Maker Fringes to Characterize Near-Surface and Bulk Second-Order Nonlinearities in Poled Silica, Applied Physics Letters, Vol. 76, No. 23, 2000, pages 3346-3348; Y. Quiquempois et al. in Localisation of the Induced Second-Order Non-Linearity Within Infrasil and Suprasil Thermally Poled Glasses, Optics Communications, Vol. 176, 2000, pages 479-487; and D. Faccio et al. in Dynamics of the Second-Order Nonlinearity in Thermally Poled Silica Glass, Applied Physics Letters, Vol. 79, No. 17, 2001, pages 2687-2689. These references are incorporated in their entirety by reference herein.
However, the previous methods do not produce a unique solution for d_{33}(z). Two rather different trial profiles can provide almost equally good fits to the measured MF data. This aspect of using fitting routines to determine d_{33}(z) is described in more detail by Alice C. Liu et al. in Advances in the Measurement of the Poled Silica Nonlinear Profile, SPIE Conference on Doped Fiber Devices II, Boston, Mass., November 1998, pages 115-119, which is incorporated in its entirety by reference herein.
According to one aspect of the present invention, a method measures a second-order optical nonlinearity profile of a sample. The method comprises providing the sample having the second-order optical nonlinearity profile. The method further comprises placing a surface of the sample in proximity to a surface of a supplemental sample. The sample and supplemental sample form a composite sample having a symmetric second-order optical nonlinearity profile. The method further comprises measuring a Fourier transform of the symmetric second-order optical nonlinearity profile. The method further comprises calculating an inverse Fourier transform of the measured Fourier transform. The calculated inverse Fourier transform provides information regarding the second-order optical nonlinearity profile.
In another aspect of the present invention, a method measures a physical function. The method comprises forming a symmetric composite function by superimposing the physical function with a substantially identical physical function. The method further comprises obtaining a Fourier transform of the symmetric composite function. The method further comprises calculating an inverse Fourier transform of the obtained Fourier transform. The calculated inverse Fourier transform provides information regarding the physical function.
In still another aspect of the present invention, a method determines the temporal waveform of a laser pulse. The method comprises providing a laser pulse having a temporal waveform. The method further comprises providing a time-reversed pulse having a time-reversed temporal waveform which corresponds to the temporal waveform of the laser pulse after being time-reversed. The method further comprises forming a symmetric composite waveform by combining the temporal waveform of the laser pulse and the time-reversed temporal waveform of the time-reversed pulse. The method further comprises obtaining a Fourier transform of the symmetric composite waveform. The method further comprises calculating an inverse Fourier transform of the obtained Fourier transform. The calculated inverse Fourier transform provides information regarding the temporal waveform of the laser pulse.
In still another aspect of the present invention, a method measures a nolinearity profile of a sample. The method comprises providing a sample having at least one sample surface and having a sample nonlinearity profile along a sample line through a predetermined point on the sample surface. The sample line is oriented perpendicularly to the sample surface. The method further comprises measuring a Fourier transform of the sample nonlinearity profile. The method further comprises providing a reference material having at least one reference surface and having a reference nonlinearity profile along a reference line through a predetermined point on the reference surface. The reference line is oriented perpendicularly to the reference surface. The method further comprises obtaining a Fourier transform of the reference nonlinearity profile. The method further comprises forming a first composite sample having a first composite nonlinearity profile by placing the sample and the reference material proximate to one another in a first configuration with the sample line substantially collinear with the reference line. The method further comprises measuring a Fourier transform of the first composite nonlinearity profile. The method further comprises forming a second composite sample having a second composite nonlinearity profile which is inequivalent to the first composite nonlinearity profile by placing the sample and the reference material proximate to one another in a second configuration with the sample line substantially collinear with the reference line. The method further comprises measuring a Fourier transform of the second composite nonlinearity profile. The method further comprises calculating the sample nonlinearity profile using the Fourier transforms of the sample nonlinearity profile, the reference nonlinearity profile, the first composite nonlinearity profile, and the second composite nonlinearity profile.
In still another aspect of the present invention, a method measures a nolinearity profile of a sample. The method comprises providing a sample having at least one sample surface and having a sample nonlinearity profile along a sample line through a predetermined point on the sample surface. The sample line is oriented perpendicularly to the sample surface. The method further comprises measuring a Fourier transform of the sample nonlinearity profile. The method further comprises providing a reference material having at least one reference surface and having a reference nonlinearity profile along a reference line through a predetermined point on the reference surface. The reference line is oriented perpendicularly to the reference surface. The method further comprises obtaining a Fourier transform of the reference nonlinearity profile. The method further comprises forming a first composite sample having a first composite nonlinearity profile by placing the sample and the reference material proximate to one another in a first configuration with the sample line substantially collinear with the reference line. The method further comprises measuring a Fourier transform of the first composite nonlinearity profile. The method further comprises forming a second composite sample having a second composite nonlinearity profile which is inequivalent to the first composite nonlinearity profile by placing the sample and the reference material proximate to one another in a second configuration with the sample line substantially collinear with the reference line. The method further comprises measuring a Fourier transform of the second composite nonlinearity profile. The method further comprises using the Fourier transforms of the sample nonlinearity profile, the reference nonlinearity profile, the first composite nonlinearity profile, and the second composite nonlinearity profile to calculate the sample nonlinearity profile.
In still another aspect of the present invention, a method measures a sample temporal waveform of a sample optical pulse. The method comprises providing a sample optical pulse having a sample temporal waveform. The method further comprises measuring a Fourier transform of the sample temporal waveform. The method further comprises providing a reference optical pulse having a reference temporal waveform. The method further comprises obtaining a Fourier transform of the reference temporal waveform. The method further comprises forming a first composite optical pulse comprising the sample optical pulse followed by the reference optical pulse. The first composite optical pulse has a first composite temporal waveform. The method further comprises measuring the Fourier transform of the first composite temporal waveform. The method further comprises providing a time-reversed pulse having a time-reversed temporal waveform corresponding to the reference temporal waveform after being time-reversed. The method further comprises forming a second composite optical pulse comprising the sample optical pulse followed by the time-reversed optical pulse. The method further comprises measuring the Fourier transform of the second composite temporal waveform. The method further comprises calculating the sample temporal waveform using the Fourier transform of the sample temporal waveform, the Fourier transform of the reference temporal waveform, the Fourier transform of the first composite temporal waveform, and the Fourier transform of the second composite temporal waveform.
For purposes of summarizing the invention, certain aspects, advantages and novel features of the invention have been described herein above. It is to be understood, however, that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the invention. Thus, the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.
In the method 100, the sample 10 is provided in an operational block 110. The sample 10 has the second-order optical nonlinearity profile 15 to be measured. In an operational block 120, a surface of the sample 10 is placed proximate to a surface of a supplemental sample 20, as schematically illustrated in
In certain embodiments, the information comprises the magnitude and sign of the second-order optical nonlinearity profile 15 as a function of depth below the surface of the sample 10. In other embodiments, information comprises the position of the second-order optical nonlinearity profile 15 below the surface of the sample 10.
In certain embodiments, the second-order optical nonlinearity profile 15 is non-symmetric, while in other embodiments, the second-order optical nonlinearity profile 15 is symmetric. Other existing methods are useful for measuring symmetric second-order optical nonlinearity profiles, but such existing methods are not compatible with non-symmetric profiles. Embodiments described herein are compatible with both symmetric and non-symmetric second-order optical nonlinearity profiles. Since it is not generally known whether the second-order optical nonlinearity profile is symmetric or non-symmetric prior to measurement, embodiments described herein provide a general method of measurement independent of the symmetry of the profile to be determined. In certain embodiments, the information comprises whether the second-order optical nonlinearity profile is symmetric or non-symmetric.
Embodiments of the present invention can be used to determine the nonlinearity profile of any optically nonlinear material (e.g., crystalline, amorphous, organic, or inorganic) in a bulk form or in a film form. In certain embodiments, the nonlinear material comprises an organic material, such as polymers and solids doped with dye molecules. In other embodiments, the nonlinear material comprises inorganic materials such as crystalline lithium niobate or amorphous materials (e.g., oxide-based, fluoride-based, or sulfide-based glasses).
In certain embodiments, the sample 10 comprises silica glass that has been poled so as to induce a second-order optical nonlinearity profile in the sample 10. For example, a fused silica wafer comprised of INFRASEL quartz glass and measuring 1″×1″×0.03″ (i.e., 2.54 cm×2.54 cm×7.62 mm) can be poled at approximately 270° C. in air by using an anode electrode placed proximate to one surface of the wafer (i.e., the anodic surface) and a cathode electrode placed proximate to the opposite surface of the wafer (i.e., the cathodic surface) to apply approximately 5 kV across the wafer for approximately 15 minutes. This procedure results in a second-order optical nonlinearity profile approximately 20-30 μm thick and localized beneath the anodic surface as described in more detail by Thomas G. Alley et al. in Space Charge Dynamics in Thermally Poled Fused Silica, Journal of Non-Crystalline Solids, Vol. 242, 1998, pages 165-176, which is incorporated herein in its entirety. Other materials and objects (e.g., optical fibers) with inherent or induced second-order optical nonlinearity profiles, and a wide range of poling conditions, are compatible with embodiments of the present invention.
In certain embodiments, the composite sample 30 is positioned so that the laser beam 42 is first incident on the sample 10, while in other embodiments, the laser beam 42 is first incident on the supplemental sample 20. In certain embodiments, the SH signal 52 is measured as a function of the incident angle θ of the laser beam 42 by rotating the composite sample 30 relative to the laser beam 42.
In the embodiment schematically illustrated in
In the embodiment schematically illustrated in
In alternative embodiments, as schematically illustrated in
In certain embodiments, placing the sample 10 proximate to the supplemental sample 20 comprises sandwiching the sample 10 and the supplemental sample 20 together. In certain such embodiments, the sample 10 and the supplemental sample 20 are clamped together, while in other embodiments, the sample 10 and the supplemental sample 20 are glued together. Other methods of placing the sample 10 proximate to the supplemental sample 20 are compatible with embodiments of the present invention.
The main mechanism believed to be responsible for the second-order optical susceptibility X^{(2) }in thermally poled silica is DC rectification of the third-order optical susceptibility X^{(3) }of silica. As described more fully by D. Faccio et al. and T. G. Alley et al. (cited above), the second-order susceptibility X^{(2) }is proportional to X^{(3)}E(z), where E(z) is the permanent electric field that develops inside the glass during poling.
The charge distribution within the glass which generates the permanent electric field E(z) can be determined from the nonlinearity profile d_{33}(z). Since the poled region is essentially a thin infinite plane, the electric field E(z) is related to the charge density ρ(z) by the one-dimensional form of Maxwell's equation, δE/δz=ρ(z)/ε, where ε is the dielectric susceptibility of the medium. Since d_{33}(z) is proportional to E(z), the charge distribution ρ(z) can be derived by differentiating the profile d_{33}(z). Applied to the nonlinearity profile of
The charge distribution ρ(z) shows an accumulation of positive charge near the surface, with a negatively charged region deeper in the sample 10. The centers of the two regions are separated by approximately 15 μm. A smaller, positively charged-region is also apparent approximately 45 μm into the sample 10. The charge distribution illustrated by
The nonlinearity profile derived in accordance with embodiments of the present invention can be independently verified by comparing the measured Maker fringe profile from the original sample 10 (shown as open circles in FIG. 5 and
Embodiments of the present invention enable the second-order nonlinearity profile of an optically nonlinear film to be inferred unambiguously from a Maker fringe profile measurement. As described above, the nonlinearity profile of an exemplary thermally poled silica sample has been determined to: (i) have a peak value of approximately −0.8 pm/V, (ii) extend approximately 25 μm below the sample surface, and (iii) take both positive and negative values. Such magnitude and spatial information of the nonlinearity profile and of the charge distribution has significant implications in the design of future devices based on thermally poled silica.
Embodiments described above can be considered to be special cases of a more general method of determining the second-order nonlinearity profile. In the embodiments described above in which the sample 10 has been cut into two pieces which form the composite sample 30, two assumptions have been made: (1) the nonlinearity profiles of both the sample 10 and the supplemental sample 20 have the same functional dependence normal to the sample surface (i.e., ƒ(z)); and (2) both the sample 10 and the supplemental sample 20 have the same nonlinear strength normal to the sample surface (i.e., d_{33}(z)=K·ƒ(z), where K is the same constant for both the sample 10 and the supplemental sample 20). These assumptions in principle limit the application of above-described embodiments to nonuniform poled samples.
In another embodiment, the nonlinearity profile of a sample is uniquely determined without either of the two assumptions described above. In addition, the sample 10 need not be cut into two pieces to determine the nonlinearity profile.
In certain embodiments, the Fourier transform of the sample nonlinearity profile is measured in the operational block 154 by measuring the Maker fringe (MF) data of the sample in a single-pass configuration as schematically illustrated by FIG. 10A. The MF data of the sample (MF_{1}) is thus representative of the Fourier transform of the sample nonlinearity profile along a sample line through a predetermined point (labelled “A” in
MF _{1}(ƒ)=|D _{A}(ƒ)|^{2} (2)
and the MF data of the reference sample is expressed as:
MF _{2}(ƒ)=|D _{B}(ƒ)|^{2} (3)
where the Fourier transform of the sample nonlinearity profile d_{A}(z) is denoted by
the Fourier transform of the reference nonlinearity profile d_{B}(z) is denoted by
and ƒ is the spatial frequency.
In certain embodiments, the Fourier transform of the first composite linearity profile is measured in the operational block 162 by measuring the MF data of the first composite sample in a double-pass configuration. In embodiments in which the first composite sample has a first configuration as schematically illustrated by one of
In certain embodiments, the Fourier transform of the second composite nonlinearity profile is measured in the operational block 166 by measuring the MF data of the second composite sample in a double-pass configuration. The configuration of the second composite sample is chosen to provide a second composite nonlinearity profile inequivalent to the first composite nonlinearity profile. For example, if the first configuration of the first composite sample is that of
The MF data of the anode-to-anode configuration of
MF _{S1} =|D _{A}|^{2} +|D _{B}|^{2}+2|D _{A} ∥D _{B}|cos (φ_{A}+φ_{B}) (4)
MF _{S2} =|D _{A}|^{2} +|D _{B}|^{2}+2|D _{A} ∥D _{B}|cos (φ_{A}+φ_{B}) (5)
MF _{S3} =|D _{A}|^{2} +|D _{B}|^{2}+2|D _{A} ∥D _{B}|cos (φ_{A}+φ_{B}) (6)
MF _{S4} =|D _{A}|^{2} +|D _{B}|^{2}+2|D _{A} ∥D _{B}|cos (φ_{A}+φ_{B}) (7)
From Equations 2, 3, 4, and 5, it can be seen that MF_{S1 }and MF_{S2 }are equivalent to one another (i.e., they have the same information in terms of φ_{A }and Φ_{B}). The extra modulation term φ_{0 }does not contribute information regarding the nonlinearity profiles since it corresponds to a modulation term due to the summed thicknesses of the sample and reference material. Similarly, MF_{S3 }and MF_{S4 }are equivalent to one another, but are inequivalent to MF_{S1}, and MF_{S2}. Thus, in certain embodiments, either MF_{S1 }or MF_{S2 }is used as a first independent source of information, and either MF_{S3 }or MF_{S4 }is used as a second independent source of information. While the description below focuses on the configurations of
For configurations of
The Fourier transforms of the sample nonlinearity profile, the reference nonlinearity profile, the first composite nonlinearity profile, and the second composite nonlinearity profile are used to calculate the sample nonlinearity profile in the operational block 168. The MF measurements corresponding to the two composite samples of
MF _{S1} =|D ^{S1}(ƒ)|^{2} =|D _{A}(ƒ)+D _{B}(−ƒ)|^{2} =∥D _{A}(ƒ)|e ^{jφ} ^{ A } ^{(ƒ)} +|D _{B}(ƒ)|e ^{−jφ} ^{ B } ^{(ƒ)}|^{2} (8)
MF _{S2} =|D ^{S2}(ƒ)|^{2} =|D _{A}(ƒ)+D _{B}(ƒ)·e ^{j2πƒL}|^{2} =∥D _{A}(ƒ)|·e ^{jφ} ^{ A } ^{(ƒ)} +|D _{B}(ƒ)|·e ^{j[φ} ^{ B } ^{(ƒ)+φ} ^{ 0 } ^{(ƒ)]}∥^{2} (9)
where φ_{0}(ƒ)=2 πƒL. Expanding the absolute value sign in Equations 8 and 9, MF_{S1 }and MF_{S2 }can be expressed as:
MF _{S1} =|D _{A}|^{2} +|D _{B}|^{2}+2|D _{A} ∥D _{B}|cos (φ_{A}+φ_{B}) (10)
MF _{S2} =|D _{A}|^{2} +|D _{B}|^{2}+2|D _{A} ∥D _{B}|cos (φ_{A}−φ_{B}−φ−φ_{0}) (11)
where, the frequency dependencies of all the functions have been dropped for convenience.
Once the four sets of MF data (MF_{1}, MF_{2}, MF_{S1 }and MF_{S2}, given by Equations 2, 3, 10, and 11, respectively) are either measured or otherwise obtained, they can be used to express the following quantities:
Note that α, β, and Δ are functions of frequency, ƒ, and are fully determined by the MF data from the sample, reference material, and the first and second composite samples. Equations 12 and 13 can be rewritten in the following form:
where m and n can take any integer value (0,±1,±2, . . . ). Note also that the output of the inverse cosine function is between 0 and π. Equations 14 and 15 can be combined to express the following quantities:
where k and l are any integers. By taking the cosine of both sides and taking their absolute values, Equations 16 and 17 can be rewritten in the following form:
Equations 18 and 19 provide useful information towards the calculation of the sample nonlinearity profile. Note that the right-hand side of both Equations 18 and 19 have the same two possible values, which are given by:
where P_{1 }and P_{2 }denote these two possible values. Notice also that if
The reverse is also true, i.e., if
Using the Fourier transforms of the sample and reference material nonlinearity profiles, the following quantities can be expressed:
region
for
whereas for
the nonzero nonlinearity
profile is in the
region.
Equations 22 and 23 are connected to Equations 18 and 19 because of the
terms. This connection can be used to remove the final ambiguity of whether
Since
is a symmetric and real function, its Fourier transform magnitude is sufficient to uniquely recover it. Note that for a real and symmetric function, the Hartley transform is the same as the Fourier transform. The same is also true for
which is also a symmetric and real function. The final ambiguity can then be removed.
In certain embodiments, the ambiguity is removed in the following manner. If
then the function 2|D_{A}|P_{1 }is going to be the Fourier transform magnitude of
(see Equation 22). If the inverse Fourier transform gives the poled region in
Otherwise,
This result can be double checked by computing the inverse Fourier transform of the Fourier transform magnitude 2|D_{A}|P_{2 }and confirming that the poled region is given by
Note finally that the inverse Fourier transforms of both Fourier transform magnitudes 2|D_{A}|P_{1 }and 2|D_{A}|P_{2 }do not at the same time give a poled region in
because either 2|D_{A}|P_{1 }or 2|D_{A}|P_{2 }has to yield a poled region in
for the function
(see Equation 23).
In certain other embodiments, the ambiguity is removed by computing the inverse Fourier transform of both 2|D_{A}|P_{1 }and 2|D_{A}|P_{2}. The results should yield two symmetric functions as shown in
Thus, it is possible to uniquely recover the two arbitrary nonlinearity profiles (d_{A}(z) and d_{B}(z)) using four sets of MF data. This result is significant since (1) the technique is applicable to even nonuniform poled samples; and (2) cutting the sample into two halves is not necessary. The technique utilizes a reference material with known MF data. In certain embodiments, obtaining the MF data of the reference material comprises measuring the MF data. In other embodiments, the MF data of the reference material is previously measured and stored in memory, and obtaining the MF data comprises reading the MF data from memory. Embodiments in which the MF data is previously stored are preferable, since the number of MF measurements will be reduced from 4 to 3. Note that it is not necessary to know the reference nonlinearity profile for this technique to work, since only its corresponding MF data is used. In addition, one can use a common reference sample to characterize a plurality of samples.
In an exemplary embodiment, the sample and reference material are cut from the same poled wafer and the MF data from the sample and reference material (given by Equations 2 and 3, respectively) are related by a constant factor (i.e., MF_{1}=C·MF_{2}). Since points A and B are from the same poled surface, it can be assumed that:
d _{A}(z)=√{square root over (C)}·d _{B}(z) (24)
It follows from Equation (24) that |D_{A}|=√{square root over (C)}·|D_{B}| and φ_{A}=φ_{B}. In this exemplary embodiment, the MF data of the second composite sample (MF_{S2}, given by Equation 11) is not required to determine the sample nonlinearity profile. This result can be seen by inserting φ_{A}=φ_{B }into Equation 11 and observing that all the phase information related to the sample nonlinearity profile is removed from Equation 11. Such embodiments are preferable because the mathematics of the solution is significantly more simple and is obtained with an experimental simplicity. In this preferred embodiment, the mathematical derivation stops at Equation 12, thereby avoiding the subsequent equations.
Using the fact that |D_{A}|=√{square root over (C)}·|D_{B}| and φ_{A}=φ_{B}, Equation 12 can be rewritten as:
The left-hand-side of Equation 25 is the Fourier transform magnitude of d_{A}(z)+d_{A}(−z) and for such real and symmetric functions, the Fourier transform magnitude is sufficient to uniquely recover the original profile. The unique recovery of the sample nonlinearity profile d_{A}(z)=√{square root over (C)}·d_{B}(z) is thus achieved using Equation 25. Note that embodiments in which C=1 yield the same solution as do embodiments in accordance with the method of FIG. 2. This result can be verified by putting C=1 in Equation 25.
Certain embodiments described above yield the sample nonlinearity profile as well as the reference nonlinearitly profile. In such embodiments, the reference material can comprise a second sample with a second sample nonlinearity profile to be measured. Thus, the nonlinearity profiles of two samples can be measured concurrently.
In certain embodiments, the same reference material can be used for measuring the nonlinearity profiles of a plurality of samples. If the same reference material is used with different samples, the measured reference nonlinearity profile should be substantially the same from each of the measurements. Comparison of the measured reference nonlinearity profiles accompanying each of the plurality of measured sample nonlinearity profiles then provides an indication of the consistency of the measurements across the plurality of samples.
Embodiments described herein can also be used to measure other physical functions.
For example, instead of forming a symmetric composite function in the spatial domain as described above in relation to the nonlinearity profile of poled silica, other embodiments form a symmetric intensity profile in the time domain by the use of time reversal. In such embodiments, the symmetric composite function can have utility where phase information is needed but unavailable (e.g., ultra-short pulse diagnosis using auto-correlators). An example of time reversal is described by D. A. B. Miller in Time Reversal of Optical Pulses by Four-Wave Mixing, Optics Letters Vol. 5, 1980, pages 300-302, which is incorporated in its entirety by reference herein.
FWM has been a subject of interest in applications such as aberration compensation, spatial information processing, frequency filtering, pulse envelope shaping, and dispersion compensation. As illustrated in
Illustratively, the temporal waveform 312 of the input pulse 310 can be written in the following form:
where u_{p}(t) is the modulation of the carrier e^{j(ω} ^{ p } ^{t−kx)}. The Fourier transform of u_{p}(t) has the following form:
Ū _{P}(ω)=∫u _{p}(t)e ^{−jωt} dt. (27)
The temporal waveform of the resultant conjugate pulse 320 has the following form:
where “c” stands for “conjugate.” Note that the k-vector of the conjugate pulse E_{c}(x,t) has the reverse sign as expected. The Fourier transform of the envelope function u_{c}(t) is defined the same way:
Ū _{c}(ω)=∫u _{c}(t)e ^{−jωt} dt. (29)
The relationship between the carrier frequencies ω_{c}, ω_{p}, as defined above, and the center frequencies ω_{pump,1 }and ω_{pump,2 }of the two pumps 340, 350 is:
ω_{pump,1}+ω_{pump,2}−ω_{p}=ω_{c} (30)
With these definitions, the envelope function u_{c}(t) can be expressed as:
u _{c}(t)=∫h(ω)Ū _{p}*(−ω)e ^{jωt} dω (31)
where h(ω) is the response function of the nonlinear material 330. For broadband conjugators (with respect to the spectrum of u_{p}(t)), h(ω) can be taken as a constant (K), giving u_{c}(t) the following form:
u _{c}(t)=K∫Ū _{p}*(−ω)e ^{jωt} dω. (32)
The foregoing forms of the envelope function u_{c}(t) were obtained using the teachings of R. A. Fischer et al. in Transient Analysis of Kerr-Like Phase Conjugators Using Frequency-Domain Techniques, Physical Review A, Vol. 23, 1981, pages 3071-3083, which is incorporated in its entirety by reference herein.
The above equations can be used to show that for continuous-wave (CW) pumping, FWM can not time-reverse pulsed fields. This property of FWM in CW pumping has been extensively studied for dispersion compensation in fiber links. Examples of such work include A. Yariv et al. in Compensation for Channel Dispersion by Nonlinear Optical Phase Conjugation, Optics Letters Vol. 4, 1979, pages 52-54, and S. Watanabe et al. in Compensation of Chromatic Dispersion in a Single-Mode Fiber by Optical Phase Conjugation, IEEE Photonics Technical Letters, Vol. 5, 1993, pages 92-95, both of which are incorporated in their entirety by reference herein.
However, pulsed pumping can be used to achieve time reversal of amplitude pulses. Following the derivation of D. A. B. Miller (cited above), u_{c}(t) can be expressed as:
u _{c}(t)=K′u _{p}*(−t+τ _{0}) (33)
where K′ and τ_{0 }are constants. The −t term in Equation 33 indicates the time reversal operation. Note that Equation 26 and Equation 30 are still valid for this case. The assumptions made in the derivation of Equation 33 are that:
In other embodiments, the time-reversed pulse 320 can be provided using holographic techniques in accordance with embodiments of the present invention. Femtosecond spectral holography can be considered as a temporal analog of the classical spatial domain holography. In classical holography, a spatial information carrying beam (signal) and a uniform reference beam interfere in a recording medium, thereby recording a hologram comprising a set of fringes. Illumination of the hologram with a uniform test beam reconstructs either a real or conjugate image of the signal beam, depending on the geometry.
Femtosecond spectral holography for the time reversal process comprises a recording phase and a read-out phase, as schematically illustrated respectively by
In the read-out phase (FIG. 16B), a short test pulse 380 is dispersed by the grating 370 and then recollimated by the lens 372. The illumination of the holographic plate 375 with this recollimated dispersed test beam 392 produces the beam 396. Using the lens 387 for recollimation and the second grating 385, a time-reversed replica 390 of the original input pulse 310 is produced. Also as a by-product, the transmitted test beam 392 appears at the output. The details of this technique are described more fully by A. M. Weiner et al. in Femtosecond Spectral Holography, IEEE Journal of Quantum Electronics, Vol. 28, 1992, pages 2251-2261, and A. M. Weiner et al. in Femtosecond Pulse Shaping for Synthesis, Processing and Time-to-Space Conversion of Ultrafast Optical Waveforms, IEEE Journal of Selected Topics in Quantum Electronics, Vol. 4, 1998, pages 317-331, both of which are incorporated in their entireties by reference herein.
The envelope of the output pulse 390 can be expressed as:
u _{out}(t)≈u _{t}(t)*u _{r}(−t)*u _{s}(t)e ^{j{overscore (K)}} ^{ 1 } ^{{overscore (r)}} +u _{t}(t)*u _{r}(t)*u _{s}(−t)e ^{j{overscore (K)}} ^{ 2 } ^{{overscore (r)}} (34)
where u_{out}(t), u_{t}(t), u_{r}(t), and u_{s}(t) are the complex envelope functions of the electric fields of the output pulse 390, test pulse 380, reference pulse 360, and input pulse 310, respectively. The sign ‘*’ denotes the convolution function, and {overscore (K)}_{1}={overscore (k)}_{t}−{overscore (k)}_{r}+{overscore (k)}_{s }and {overscore (K)}_{2}={overscore (k)}_{t}+{overscore (k)}_{r}−{overscore (k)}_{s}.
When the test pulse 380 and the reference pulse 360 are considerably shorter than the input pulse 310, u_{s}(t), u_{t}(t), and u_{r}(t) will act as delta functions with respect to u_{s}(t), modifying the envelope of the output pulse 390 to be:
u _{out}(t)≈u _{s}(t)e ^{j{overscore (K)}} ^{ 1 } ^{{overscore (r)}} +u _{s}(−t)e ^{j{overscore (K)}} ^{ 2 } ^{{overscore (r)}}. (35)
Therefore, as a result of the illumination of the holographic plate with the test pulse 380, the output pulse 390 serves as the time-reversed signal pulse 320 in the {overscore (K)}_{2 }direction. As described below, the apparatus schematically illustrated by
Note that embodiments of both the pulse-pumped FWM and the spectral holography techniques use shorter pulses than the input pulse 310 to time-reverse the input pulse 310. For pulse-pumped FWM, shorter pump pulses 340, 350 are used, and for holography, shorter test pulses 380 and reference pulses 360 are used.
In certain embodiments for estimating the temporal waveform of a laser pulse, a classical correlator configuration is used with a second-harmonic generating (SHG) crystal 510.
The third pulse 524 emerging from one arm of the Michelson interferometer 500 has a waveform given by:
E _{1}(t)=u _{1}(t)e ^{jωt} (36)
where u_{1}(t) is the complex envelope function of the input pulse 310. The fourth pulse 526 emerging from the other arm of the Michelson interferometer 500 has a waveform given by:
E _{2}(t)=u _{2}(t)e ^{jωt} =u _{1}(t−τ)e ^{jω(} t−τ) (37)
where τ is the relative time delay between the third pulse 524 and the fourth pulse 526 imposed by the delay τ between the two arms. Because of the focusing lens 540, the third pulse 524 and the fourth pulse 526 have different k-vectors at the surface of the SHG crystal 510. Consequently, the SH field 538 generated by the SHG crystal 510 that is not blocked by the pinhole 560 includes only terms due to the interaction of the third pulse 524 and the fourth pulse 526, and has a waveform given by:
E _{2ω}(t)=u _{2ω}(t)e ^{j2ωt} =ηu _{1}(t)u _{2}(t)e ^{j2ωt} =ηu _{1}(t)u _{1}(t−τ)e ^{−jωτ} e ^{j2ωt} (38)
where η is a conversion efficiency factor corresponding to the SHG crystal and the system geometry. The signal detected by the photomultiplier 580 (i.e., the autocorrelation function) is given by:
A _{PMT}(τ)=∫E _{2ω}(t)E _{2ω}*(t)dt=∫|η| ^{2} |u _{1}(t)|^{2} |u _{1}(t−τ)|^{2} dt=|η| ^{2} ∫I(t)I(t−τ)dt (39)
where I(t)=|u_{1}(t)|^{2 }is the input signal intensity. In general, η is a function of frequency and the functions u_{1}(t) and u_{2}(t) can be expanded as plane waves with Fourier transform amplitudes (i.e., u_{i}(t)=∫Ū_{i}(ω)e^{jωt}dω). However, it is assumed here that η is constant over the frequency range of the combined pulses, which is equivalent to assuming that X^{(2) }is independent of frequency. This assumption holds when the effective crystal length is shorter than the coherence length of the harmonic generation over the pulse bandwidth.
By taking the Fourier transform of both sides of Equation 39 (the signal detected by the photomultiplier 580 for a single pulse) provides the Fourier transform of the autocorrelation function and is given by:
Ā _{PMT} _{ — } _{single}(ƒ)=|η|^{2} |Ī(ƒ)|^{2} (40)
where Ā_{PMT} _{ — } _{single}(ƒ) and Ī(ƒ) are the Fourier transforms of A_{PMT}(τ) and I (τ), respectively. Thus, the signal from the Michelson interferometer 500 of
However, the magnitude of the Fourier transform is not sufficient information to retrieve uniquely the input pulse intensity I(t). To do so would also require the knowledge of the phase of the Fourier transform, which this classical autocorrelation method does not provide. This difficulty in uniquely determining the input pulse intensity I(t) is analogous to that of retrieving the second-order susceptibility spatial profile of a nonlinear material, as described above. In practice, a number of methods can be used to avoid this difficulty. For example, a certain shape for the pulse intensity (e.g., a Gaussian) can be assumed, but there is no way to independently verify that the assumed shape is the true temporal waveform. This method therefore provides only an estimate of the pulse shape.
By using a time-reversal technique compatible with embodiments of the present invention (e.g., pulse-pumped FWM or femtosecond spectral holography), a time-reversed pulse with a time-reversed temporal waveform I(−t) of the temporal waveform I(t) of an arbitrary pulse can be produced. A symmetric composite waveform can then be formed by delaying the time-reversed pulse with respect to the original pulse and combining the temporal waveform with the time-reversed temporal waveform, for example with a beamsplitter.
The symmetric composite waveform 650 has the following form:
where Δt is the variable time delay between the time-reversed pulse 652 and the original pulse 622. The Fourier transform of Equation 41 is given by:
Since I(t) is real, |Ī(ƒ)|=|Ī(−ƒ)| and Φ(ƒ)=−Φ(ƒ), where Ī(ƒ) has been defined as: Ī(ƒ)=|Ī(ƒ)|e^{jφ(ƒ)}. Using these identities, together with Equations 40 and 42, the Fourier transform of the autocorrelation function corresponding to the symmetric composite waveform 650 has the following form:
Ā _{PMT} _{ — } _{double}(ƒ)=2|η| ^{2} |Ī(ƒ)|^{2}|1+cos (2φ(ƒ)−ƒΔt)|. (43)
In embodiments in which Ā_{PMT} _{ — } _{double }is real and greater than zero for all frequencies ω (i.e., there are no zero crossings of Ā_{PMT} _{ — } _{double }from the cosine term), then the inverse Fourier transform of Equation 43 provides the intensity of the symmetric pulse sequence 650 without any ambiguity. Once the intensity of the symmetric pulse sequence 650 is calculated in this way, the intensity of the original pulse can be found by separating the pulse 650 in the middle.
In the following, an embodiment is illustrated analytically by showing the result of numerical simulations using the input pulse of FIG. 19. First, the time-reversal of the input pulse is obtained using one of the phase conjugate mirror schemes described above.
In the second step, the autocorrelator of
In the third step, the function g(ƒ)=1+cos(2φ(ƒ)−ƒΔt) is determined by dividing both sides of Equation 43 by |Ī(ƒ)|^{2}. From the knowledge of g(ƒ)−1, the function
can be determined. Using Equation 42, the Fourier transform of the symmetric temporal waveform can be expressed as:
Therefore, since |Ī(ƒ)| is known from
To determine the function
from the function
two possible cases can be analyzed. In the first case, if there are no zero crossings of the term
then there is no ambiguity due to the absolute value sign since intensity has to be non-negative (−I_{symmetric}(t) is not a possible solution). In the second case, if there are some zero crossings of the term
the sign ambiguities of the cosine term between the zero crossings can be removed by using a property of Fourier transforms. For a real and symmetric function such as I_{symmetric}(t), the Fourier transform Ī_{symmetric}(ƒ) is equivalent to the Hartley transform
Therefore, the magnitude of the Hartley transform of I_{symmetric}(t) (i.e.,
can be determined from the knowledge of
and |Ī(ƒ)|. For a real and compact support function (i.e., one that equals zero outside a finite region), such as I_{symmetric}(t), the intensity of the Hartley transform is enough to uniquely recover the original function. See, e.g., N. Nakajima in Reconstruction of a real function from its Hartley-transform intensity, Journal of the Optical Society of America A, Vol. 5, 1988, pages 858-863, and R. P. Millane in Analytic Properties of the Hartley Transform and their Implications, Proceedings of the IEEE, Vol. 82, 1994, pages 413-428, both of which are incorporated in their entirety by reference herein.
An arbitrary input pulse 710 has the following form:
u _{s}(t)=ũ_{s}(t)e ^{jω} ^{ c } ^{t} (45)
where ũ_{s}(t) is the complex envelope function and ω_{c }is the carrier frequency. Equation 45 can be rewritten as:
u _{s}(t)=∫Ũ _{s}(ω−ω_{c})e ^{jωt} dω (46)
where Ũ_{s}(ω) denotes the Fourier transform of ũ_{s}(t). The input pulse 710 is decomposed by the grating 720 into several monochromatic plane waves with amplitudes Ũ_{s}(ω−ω_{c}). By finding the response of the system 700 to each individual harmonic component (i.e. Ũ_{s}(ω−ω_{c})e^{jωt}), the overall response of the system 700 can be determined using the integral given in Equation 46.
The field of a single harmonic Ũ_{s}(ω−ω_{c})e^{jωt }at the plane 722 immediately after being dispersed by the grating 720 can be written in the following form:
where w(x) is the pupil function of the optical field on the grating 720, c is the speed of light, x is the coordinate along the plane 722, and θ is the incident angle of the input pulse 710 to the grating 720. This form of the single harmonic field is described by P. C. Sun et al. in Femtosecond Pulse Imaging: Ultrafast Optical Oscilloscope, Journal of the Optical Society of America, Vol. 14, 1997, pages 1159-1170, which is incorporated in its entirety by reference herein.
The last exponential term of Equation 47 accounts for the diffraction experienced by the spectral components of the input pulse 710 due to the grating 720, assuming only first-order diffraction. The grating 720 is arranged such that the first diffraction order for the spectral component at ω=ω_{c }propagates along the direction of the optical axis of the system 700. The lens 730 transforms the image at the plane 722 into an image at plane 742. The fields at the two planes 722, 742 are related by a spatial Fourier transform. By taking the spatial Fourier transform of Equation 23, the field at the plane 742 can be written as:
where W(ƒ_{x′}) is the spatial Fourier transform of w(x). x′ is the coordinate along the plane 742, and ƒ_{x′} is the spatial frequency which can be written as:
where F is the focal length of the lens.
The total response of the system 700 is the spectral decomposition of the field u_{s}(t) of the input pulse 710 and can be found by integrating Equation 48 over the frequency range, i.e.,:
u _{2s}(x ^{1} ;t)=∫Ũ _{2s}(x′;ω,t)dω (50)
By using the paraxial approximation and by assuming a large illumination window w(x), the total response given by Equation 50 can be simplified to the following form:
By generating a phase conjugate pulse as schematically illustrated in
u _{total}(t)=(ũ _{s}(t)+ũ _{s}*(−t−Δt))e ^{jω} ^{ c } ^{t} (52)
where Δt is the time delay between the original pulse and its corresponding phase conjugate pulse. Feeding this total field into the system 700 illustrated in
The CCD imaging device 740 at the plane 742 is responsive to intensity, which can be written as:
I(x′)=∫|u _{total,2}(x′;t)|^{2} dt. (54)
Defining Ũ_{s}(ω)=|Ũ_{s}(ω)|e^{jΦ(ω) }and A=−F sin θ, Equation 54 can be rewritten as:
Furthermore, Equation 55 can be rewritten as:
with
Equation 56 is very similar to Equation 43, which was obtained for embodiments utilizing the intensity correlator of FIG. 17. Furthermore, the intensity profile on the CCD imaging device 740 for a single pulse u_{s}(t) can be expressed as:
Equation 57 is also very similar to Equation 40, which was derived above in relation to the intensity correlator embodiment as shown in FIG. 17.
To recover the complex envelope function ũ_{s}(t), as defined in Equation 45, the same algorithm described above for recovering I(t) can be applied. This process is illustrated in the
In a second step, the system of
In a third step, and as discussed above in relation to determining I(t) using the intensity correlation configuration of
Therefore, using the same process as described above in relation to Equation 43, the system 700 of
As described above, the waveform of an ultra-short optical pulse is determined in certain embodiments by using time-reversal techniques to yield a time-reversed replica of the pulse and to obtain a symmetric optical pulse. The Fourier transform magnitude of the symmetric optical pulse is used to uniquely recover the original time-domain optical pulse waveform. Such time-reversal techniques utilize shorter optical pulses with respect to the input optical pulse waveform being measured. For example, to determine the temporal pulse waveform of a femtosecond-scale optical pulse, sub-femtosecond-scale pulses are used to form the symmetric optical pulse waveform by time reversal.
This experimental limitation of using pulses shorter than the input pulse waveform can present a challenge which can hinder the application of the method in certain circumstances. However, in certain embodiments, a method determines the temporal waveform of an optical pulse using the Fourier transforms of four pulse waveforms and avoiding the limitation of short pulses.
The sample optical pulse of certain embodiments can have an ultra-short temporal waveform (e.g., on the order of femtoseconds or sub-femtoseconds). The reference optical pulse of certain embodiments can have a temporal waveform which is significantly more broad than the temporal waveform of the sample optical pulse. For example, for a femtosecond sample temporal waveform, the width of the reference temporal waveform can be on the order of nanoseconds. By allowing the use of reference optical pulses with broader temporal waveforms, embodiments of the present invention allow for easier time-reversal processes, since the optical pulses used to time-reverse the reference optical pulse can be correspondingly broader. In certain such embodiments, the sample optical pulse itself can be used to time-reverse the reference optical pulse.
In certain embodiments, the first composite optical pulse includes a time delay between the sample optical pulse and the reference optical pulse. In certain such embodiments, the time delay can be adjusted to make the measurement of the Fourier transform easier. The time delay used can be dependent upon the particular technique used to measure the Fourier transform. Similarly, in certain embodiments, the second composite optical pulse includes a time delay between the sample optical pulse -and the time-reversed optical pulse, and the time delay can be adjusted to ease the measurement of the Fourier transform depending on the particular measurement technique used.
In certain embodiments, the Fourier transforms of the sample temporal waveform, the reference temporal waveform, the first composite temporal waveform, and the second composite temporal waveform are measured using an auto-correlator as described above, or using other holographic techniques. In certain embodiments, obtaining the Fourier transform of the reference temporal waveform comprises measuring the Fourier transform. In other embodiments, the Fourier transform of the reference temporal waveform is previously measured and stored in memory, and obtaining the Fourier transform comprises reading the Fourier transform from memory.
Using the four Fourier transforms in the same manner as described above for measuring the sample nonlinearity profile, the sample temporal waveform can be measured. Note that the reference temporal waveform can also be calculated by embodiments of the present invention concurrently with the calculation of the sample temporal waveform. However, because the reference optical pulse is temporally broad, its temporal waveform is of less interest than that of the sample optical pulse. In embodiments in which the same reference optical pulse is used to measure the temporal waveforms of a series of sample optical pulses, the calculated series of reference temporal waveforms can be compared to one another, thereby providing a check of the validity of the measurements across the series of calculations.
This invention may be embodied in other specific forms without departing from the essential characteristics as described herein. The embodiments described above are to be considered in all respects as illustrative only and not restrictive in any manner. The, scope of the invention is indicated by the following claims rather than by the foregoing description. Any and all changes which come within the meaning and range of equivalency of the claims are to be considered within their scope.
Cited Patent | Filing date | Publication date | Applicant | Title |
---|---|---|---|---|
US4792230 | Sep 8, 1987 | Dec 20, 1988 | Nippon Telegraph And Telephone Corporation | Method and apparatus for measuring ultrashort optical pulses |
US5086239 * | Feb 22, 1990 | Feb 4, 1992 | E. I. Du Pont De Nemours And Company | Nonlinear optical elements containing j-aggregates of aromatic dyes |
US5194918 * | May 14, 1991 | Mar 16, 1993 | The Board Of Trustees Of The Leland Stanford Junior University | Method of providing images of surfaces with a correlation microscope by transforming interference signals |
US5420717 * | Feb 17, 1993 | May 30, 1995 | Olympus Optical Co., Ltd. | Adjustable-contrast microscope |
US5530544 | Aug 31, 1994 | Jun 25, 1996 | Sandia Corporation | Method and apparatus for measuring the intensity and phase of one or more ultrashort light pulses and for measuring optical properties of materials |
US6043884 * | Jul 28, 1998 | Mar 28, 2000 | Bio-Rad Laboratories, Inc. | DSP technique for photoacoustic spectroscopy (PAS) sample pulse response for depth profiling |
US6456380 | May 15, 2000 | Sep 24, 2002 | Nippon Telegraph And Telephone Corporation | Method and apparatus for measuring waveform of optical signal |
JP2000329618A | Title not available | |||
JP2001083015A | Title not available | |||
WO2004019018A2 | Aug 21, 2003 | Mar 4, 2004 | The Board Of Trustees Of The Leland Stanford Junior University | Method of measuring nonlinearity spatial profiles of samples and temporal profiles of optical pulses |
Reference | ||
---|---|---|
1 | "Invitation to Pay Additional Fees" from the International Searching Authority regarding corresponding PCT Application No. PCT/US 03/26311, filed Aug. 21, 2003, including Annex to Form PCT/ISA/206, "Communication Relating to the Results of the Partial International Search". | |
2 | Alley, Thomas G., et al., Space charge dynamics in thermally poled fused silica, Journal of Non-Crystalline Solids 242 (1998), pp. 165-176. | |
3 | Bonfrate, G. et al., Parametric fluorescence in periodically poled silica fibers, Applied Physics Letters, vol. 75, No. 16, Oct. 18, 1999, pp. 2356-2358. | |
4 | Faccio, D., et al., Dynamics of the second-order nonlinearity in thermally poled silica glass, Applied Physics Letters, vol. 79, No. 17, Oct. 22, 2001, pp. 2687-2689. | |
5 | Ferreira, Paulo Jorge S.G., Interpolation and the Discrete Papoulis-Gerchberg Algorithm, IEEE Transactions on Signal Processing, vol. 42, No. 10, Oct. 1994, pp. 2596-2606. | |
6 | Fisher, Robert A., et al., Transient analysis of Kerr-like phase conjugators using frequency-domain techniques, Physical Review A, vol. 23, No. 6, Jun. 1981, pp. 3071-3083. | |
7 | Kashyap, Raman, et al., Phase-matched second harmonic generation by periodic poling of fused silica, Applied Physics Letters, vol. 64, No. 11, Mar. 14, 1994, pp. 1332-1334. | |
8 | Kazansky, P.G., et al., Thermally poled silica glass: Laser induced pressure pulse probe of charge distribution, Applied Physics Letters, vol. 68, No. 2, Jan. 8, 1996, pp. 269-271. | |
9 | Liu, Alice C., et al., Advances in the measurement of the poled silica nonlinear profile, SPIE vol. 3542, Nov. 1998, pp. 115-119. | |
10 | Maker, P.D., et al., Effects of Dispersion and Focusing on the Production of Optical Harmonics, Physical Review Letters, vol. 8, No. 1, Jan. 1, 1962, pp. 21-22. | |
11 | Millane, R.P., Analytic Properties of the Hartley Transform and their Implications, Proceedings of the IEEE, vol. 82, No. 3, Mar. 1994, pp. 413-428. | |
12 | Miller, D.A.B., Time reversal of optical pulses by four-wave mixing, Optics Letters, vol. 5, No. 7, Jul. 1980, pp. 300-302. | |
13 | Myers, R.A., et al., Large second-order nonlinearity in poled fused silica, Optics Letters, vol. 16, No. 22, Nov. 15, 1991, pp. 1732-1734. | |
14 | Nakajima, N., Reconstruction of a real function from its Hartley-transform intensity, J. Opt. Soc. Am. A., vol. 5, No. 6, Jun. 1988, pp. 858-863. | |
15 | Ozcan, A., et al., Inverse Fourier transform technique to determine second-order optical nonlinearity spatial profiles, Applied Physics Letters, vol. 82, No. 9, Mar. 3, 2003, pp. 1362-1364. | |
16 | Pureur, D., et al., Absolute measurements of the second-order nonlinearity profile in poled silica, Optics Letters, vol. 23, No. 8, Apr. 15, 1998, pp. 588-590. | |
17 | Qiu, Mingxin, et al., Double fitting of Maker fringes to characterize near-surface and bulk second-order nonlinearities in poled silica, Applied Physics Letters, vol. 76, No. 23, Jun. 5, 2000, pp. 3346-3348. | |
18 | Qui, Mingxin, et al., Erratum: "Double fitting of Marker fringes to characterize near-surface and bulk second-order nonlinearities in poled silica," Applied Physics Letters, vol. 77, No. 23, Dec. 4, 2000, p. 3863. | |
19 | Quiquempois, Y., et al., Localisation of the induced second-order non-linearity within Infrasil and Suprasil thermally poled glasses, Optics Communications 176, Apr. 1, 2000, pp. 479-487. | |
20 | Sun, P.C. et al., Femtosecond pulse imaging: ultrafast optical oscilloscope, J. Opt. Soc. Am. A, vol. 14, No. 5, May 1997, pp. 1159-1170. | |
21 | Watanbe, Shigeki, et al., Compensation of Chromatic Dispersion in a Single-Mode Fiber by Optical Phase Conjugation, IEEE Photonics Technology Letters, vol. 5, No. 1, Jan. 1993, pp. 92-95. | |
22 | Weiner, Andrew M., et al., Femtosecond Pulse Shaping for Synthesis, Processing, and Time-to-Space Conversion of Ultrafast Optical Waveforms, IEEE Journal of Selcted Topics in Quantum Electronics, vol. 4, No. 2, Mar./Apr. 1998, pp. 317-331. | |
23 | Weiner, Andrew M., et al., Femtoseconnd Spectral Holography,IEEE Journal of Quantum Electronics, vol. 28, No. 10, Oct. 1992, pp. 2251-2256. | |
24 | Yariv, Amnon, et al., Compensation for channel dispersion by nonlinear optical phase conjugation, Optics Letters, vol. 4, No. 2, Feb. 1979, pp. 52-54. |
Citing Patent | Filing date | Publication date | Applicant | Title |
---|---|---|---|---|
US7050169 | Aug 21, 2003 | May 23, 2006 | The Board Of Trustees Of The Leland Stanford Junior University | Method of measuring a physical function using a composite function which includes the physical function and an arbitrary reference function |
US7133134 | Jan 31, 2003 | Nov 7, 2006 | The Board Of Trustees Of The Leland Stanford Junior University | Method of measuring a physical function using a symmetric composite function |
US7236246 | Feb 16, 2006 | Jun 26, 2007 | The Board Of Trustees Of The Leland Stanford Junior University | Method of measuring a physical function using a composite function which includes the physical function and an arbitrary reference function |
US7236247 | Feb 16, 2006 | Jun 26, 2007 | The Board Of Trustees Of The Leland Stanford Junior University | Method of measuring a physical function using a composite function which includes the physical function and an arbitrary reference function |
US7259868 * | Nov 23, 2004 | Aug 21, 2007 | The Board Of Trustees Of The Leland Stanford Junior University | Method for determining the optical nonlinearity profile of a material |
US7365851 * | May 10, 2007 | Apr 29, 2008 | The Trustees Of The Leland Stanford Junior University | Method of measuring a physical function using a composite function which includes the physical function and an arbitrary reference function |
US7417742 * | Aug 20, 2007 | Aug 26, 2008 | The Board Of Trustess Of The Leland Stanford Junior University | Method for estimating the optical nonlinearity of a material |
US20040036880 * | Jan 31, 2003 | Feb 26, 2004 | Aydogan Ozcan | Method of measuring a physical function using a symmetric composite function |
US20040133614 * | Aug 21, 2003 | Jul 8, 2004 | Aydogan Ozcan | Method of measuring a physical function using a composite function which includes the physical function and an arbitrary reference function |
US20050111002 * | Nov 23, 2004 | May 26, 2005 | Aydogan Ozcan | Method for determining the optical nonlinearity profile of a material |
US20060132783 * | Feb 16, 2006 | Jun 22, 2006 | Aydogan Ozcan | Method of measuring a physical function using a composite function which includes the physical function and an arbitrary reference function |
US20060139645 * | Feb 16, 2006 | Jun 29, 2006 | Aydogan Ozcan | Method of measuring a physical function using a composite function which includes the physical function and an arbitrary reference function |
US20070211253 * | May 10, 2007 | Sep 13, 2007 | The Board Of Trustees Of The Leland Stanford Junior University | Method of measuring a physical function using a composite function which includes the physical function and an arbitrary reference function |
US20070282569 * | Aug 20, 2007 | Dec 6, 2007 | Aydogan Ozcan | Method for estimating the optical nonlinearity of a material |
U.S. Classification | 356/432, 356/614, 359/359 |
International Classification | G01N21/63, G01J11/00 |
Cooperative Classification | G01N21/21, G01N2021/4723, G01N21/4788, G01J11/00, G01N2021/4735, G01N21/636 |
European Classification | G01N21/21, G01N21/47H, G01N21/63H, G01J11/00 |
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